In case a mobile radio communication terminal device such as a User Equipment (UE) leaves a Third Generation (3G) mobile radio coverage and enters a Second Generation (2G) mobile radio coverage, it needs to be ready to handover from 3G to 2G as fast as possible since the 3G coverage may disappear quickly. If a suitable 2G mobile radio cell a handover can be executed to cannot be found in time, the mobile radio call will drop.
A conventional implementation is done according to the 3GPP mobile radio communication standards for 2G mobile radio measurements in the so-called 3G dedicated mode.
In a first mode of the 3G dedicated mode, it is provided that the mobile radio network only activates so-called mobile radio compressed mode transmission gaps for “GSM carrier RSSI measurements”. In such a scenario, a conventional implementation is as follows:
The UE measures the received signal strength indication (RSSI) of all configured 2G mobile radio cells three times, in other words, the UE gets three RSSI measurement samples for all configured 2G mobile radio cells. After the three RSSI measurements have been completed, the UE sorts the 2G mobile radio cells based on the averaged RSSI measurement result, in other words, based on the averaged three RSSI measurement samples. Then, the UE sends an RSSI measurement report to the mobile radio network. Furthermore, the UE continues measuring the RSSI of all configured 2G mobile radio cells.
In a second mode of the 3G dedicated mode, it is provided that the mobile radio network activates so-called mobile radio compressed mode transmission gaps for “GSM carrier RSSI measurements” and at least transmission gaps for “GSM initial BSIC identification”. In such a scenario, a conventional implementation is as follows:
The UE measures the received signal strength indication (RSSI) of all configured 2G mobile radio cells three times using the “GSM carrier RSSI measurements” transmission gaps, in other words, the UE gets three RSSI measurement samples for all configured 2G mobile radio cells. After the three RSSI measurements have been completed, the UE sorts the 2G mobile radio cells based on the averaged RSSI measurement result, in other words, based on the averaged three RSSI measurement samples per mobile radio cell. Then, the UE selects the strongest mobile radio cell from the sorted list and starts base station identity code (BSIC) identification procedure using the “GSM initial BSIC identification” transmission gaps. If BSIC is identified, a report containing the identified 2G mobile radio cell is sent to the mobile radio network. Furthermore, the UE continues to measure the RSSI of all configured 2G mobile radio cells. The UE continues BSIC identification on other 2G mobile radio cells, and if compressed mode transmission gaps with the purpose “GSM BSIC re-confirmation” are activated, the UE performs BSIC verification procedure on mobile radio cells with a known BSIC, in other words, a BSIC verification is performed if the corresponding transmission gap pattern is configured.
A UE requiring compressed mode shall perform the RSSI measurement in compressed mode transmission gaps with the assigned purpose being “GSM carrier RSSI measurement”. Depending on the number of 2G neighbor mobile radio cells assigned by the mobile radio network to the UE, collecting three measurement samples for all GSM neighbor mobile radio cells before being ready to start synchronisation to the strongest GSM neighbor mobile radio cell, can be a time consuming process. This contributes to the overall time the UE needs to be ready to handover to GSM and a suitable GSM neighbor mobile radio cell and increases the risk of a call drop.